Party Fish

Party Fish

December 11, 2020

It’s fun to get a party favor after a birthday party. Well, imagine if that favor was a live fish. That happened here at Bedtime Math: at a friend’s party, every one of the 32 kids took home a plastic bag of water with a confused fish swimming inside. Of course, each fish then needed the right set-up in its new home: a fishbowl or aquarium, a layer of colorful gravel (little stones), and then a cute castle or seashells for decoration…maybe even a few fish friends. Fishbowls also need the right amount of water: the rough rule is “1 gallon per inch of fish” when lined up end to end. We hope all 32 fish like their new homes!

Wee ones: If after the party you get a fish and 3 seashells, what numbers do you say to count your party favors?

Little kids: If you have 2 pet goldfish that are each 3 inches long, how many total inches long are they together?  Bonus: If they were each 5 inches long, would 9 gallons of water be enough? (Remember, you need 1 gallon per total inch…)

Big kids: If 13 of the 32 fish got a new fish buddy once home, how many total fish do the partygoers have now?  Bonus: If every 5th fish owner (starting with the 5th) bought a castle, how many castles did the store sell?

The sky’s the limit: The rule for giving fish water is 1 gallon per inch of fish. If your local pet store sells 2-inch and 5-inch tropical fish, and your fishtank can hold 20 gallons, how many different combos of fish would use exactly the full 20?












Wee ones: 1, 2, 3, 4.

Little kids: 6 inches.  Bonus: Not quite, since they would need 10 gallons.

Big kids: 45 fish.  Bonus: 6 castles, for the 5th, 10th, 15th, 20th, 25th, and 30th fish owners.

The sky’s the limit: Just 3 different combos: 10 small fish, 2 big fish and 5 small, and 4 big fish. We can’t have 1 big fish or 3 big fish, because they’d require an odd number of gallons, leaving an odd number that can’t be filled by 2s.

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